THE RAINFALL IN DIFFERENT SECTIONS.

87

Pampas, the Steppes of Russia and Siberia, and the Deserts of Asia, Africa and Australia, it may be considered a true one. It is confirmed very emphatically by the measure of the rainfall in different parts of the Valley. The table of rainfall for the subordinate basins of the Mississippi shows that the Valley of the Ohio receives, on the average, more than twice as much as that of the Missouri. It it quite certain that the character of the soil has something to do with the distribution of the prairie and timber east of the Mississippi, and even the Missouri, yet it seems an incidental influence compared with the more determining and decisive point of the average measure of rainfall.

66

There is, also, as the rain thins out westward, an increasing inequality of rain (as an average) for the different seasons of the year. The law regulating the winds and the clouds (the details of which would be too lengthy for this place) cause seventy-five per cent of the rains that fall on the Western prairies, or plains," to occur in Spring and Summer when most needed for herbage and agriculture. A nearly even distribution for each season, as in the Atlantic regions, would be fatal to agricultural success. A favorable form of the structure of New Mexico and Colorado increases the amount of moisture they receive.

It will thus be seen that the form of the Valley and its relations to the Gulf of Mexico, the high relief of the coast of Mexico and Central America, and the relations of the Gulf to the Atlantic Ocean have a most important influence on its winds and rainfall, and thereby on the remarkable fruitfulness of its soil. The general course of the winds during the productive months of the year from the South, or warmer latitudes, also gives a semi-tropical character to the climate of the Valley far to the North, and extends the productive regions of the interior of the continent almost into the center of British America. The depression in that direction to the Arctic Ocean also renders the Winters more severe, while it extends further South the region of the most useful grains.

Most of the relations of the Valley, within and without, are admirable. Its farthest extremities are brought into relation with the center and the South by the Missouri and Ohio; the long string of the Great Lakes connects much of its most fruitful region with the East by the break of the mountain chains in New York, and the Gulf gives still more perfect and immediate commercial relations with the outside world. The southern Valley is compensated for its failure to receive a general covering of the valuable drift by its greater humidity and warmth and excellent commercial position, while the central and northern parts are indemnified for their isolation in the center of the continent by their extraordinary fertility, singularly favorable climate and double system of waterways, and their vast levels invite the extraordinary development of railways they have recently received.

With these favorable circumstances is joined another of singular consequence to the speedy unfolding of all its advantages; an unusual readiness to open its various sources of wealth in all their magnitude. The seasons are long and the climate favorable to perfection of vegetable growth, while the evenness of the surface, the softness of the soil and its freedom to so large an extent from forests, promote speedy, excellent and large returns to the agriculturist. Its minerals lie at once near the surface of the earth, and, usually, near the readiest and cheapest means of transport. Various favorable conditions invite and reward enterprise in industry, manufactures and commerce to a degree unknown together in any other section of the world. Nature is here in her freest and most open-handed mood from whatever point she is viewed.

CHAPTER VIII.

THE MINERAL TREASURES OF THE VALLEY.

The highest kind of power known to us is that which belongs to mind; that which organizes matter into living forms and so confers on it new offices and capabilities, is next lower, beneath which is the power residing in chemical attraction and repulsion; the mechanical force or weight of matterwhich measures the power of the attraction called gravitation -being the lowest. Intelligence has evidently superintended the operation of the lower forms of power, from first to last, and probably they are merely the modes in which the Supreme Intelligence displays its energy.

The earth has ever been a vast chemical laboratory. Mental and organic powers are scarcely more wonderful or mysterious than chemical force, and they seem dependent on it, in some form, for each of their innumerable manifestations. It is to this active agent and its extraordinary properties that the vast mineral accumulations of the Valley are due. It has acted with the greatest vigor where heat and moisture were abundant, and therefore its most stupendous deeds were accomplished in the early ages of the World, when the crust was thin, when the internal heat of the earth could make itself powerfully felt on the surface, and while the surface of the Valley was largely covered with water. The largest amount of mineral stores was usually accumulated at the point where these two elements met.

Most of the metals have been collected in large quantities by means of water heated by volcanic, or by chemical, forces and therefore along the lines where volcanic energies broke out. Yet, the largest accumulations of iron, the production

of coal and perhaps of lead, did not require, apparently, any great degree of volcanic heat for their immediate deposit. Here the more remote and gradual operations of heat led to› the final result. Chemistry, as well as vital force, has had a graduated development to a certain extent. It had its special periods for the accomplishment of various tasks. Rocks of a certain composition could only be produced under certain circumstances, and different classes of metals must wait their turn to be gathered in large masses. There was a constant succession of services performed by chemistry for our Valley through the geological ages.

Iron is diffused very widely and abundantly through the rocks under many combinations. It is thought by some that the proportion is still larger in the center of the earth and even that it may constitute two thirds of the mass of the earth. The composition of the meteors-mostly iron-that have reached the earth from other spheres suggests this view, in which case the earth may be considered as ballasted with iron, and to have embodied in its true crust the larger quantity of its various other and lighter mineral substances.

Iron was specially abundant in the Azoic and primary rocks and the largest and purest beds date from that time. It is thought that beds of iron are always due to the chemical action of decomposed vegetable matter. The deposits of iron now being made are all accomplished in this way and it seems probable that it has always been done in the same manner, and that masses of this metal are both the evidence and the measure of the vegetation of the time and place of deposit. In this case evidence would be furnished of an extreme abundance of plant life on what have been usually called the Azoic rocks. The largest beds of iron known, and of a purity and excellence nowhere surpassed, lie along the south shore of Lake Superior. They are in the group of rocks formed immediately before the first of those known as Palæozoic, which contain the first well-preserved forms of ancient

THE IRON ORES OF THE VALLEY.

91 animals. At that time this region was the southern shore line of the early continent.

Iron was more abundant, or more concentrated, in the early or Archæan rocks, and probably the vegetation of the time was chiefly seaweeds, lichens and possibly the coarse vegetation of marshes. The rains and streams leached out and washed down the iron of the surface rock of the land under various combinations, and the decaying vegetation of the bogs and marshes of the shore caused it to be deposited in great abundance and purity at these points. It is said to equal in quality the best ores of the Old World, while the largest single deposits of that continent would be mere patches compared to the extent of this. The area of the Lake Superior mines is about 150 miles in length from east to west by a varying breadth of from six to seventy miles. Stretching along the shore of the lake the ore is peculiarly well situated for cheap and easy transport to the vicinity of the best and most abundant coals of Ohio and Pennsylvania.

Iron, apparently of the same age, is largely developed in Missouri-the very center of the Valley, and not distant from suitable coals for working it. Iron of this age is also found in Arkansas, in New York and New Jersey. Beds of it formed in various ages, and especially in the great Coal Age, are found in most parts of the country and very frequently in the neighborhood of coal areas. Although not so pure or so high in quality, it serves ordinary purposes well and is obtained and worked at a minimum of expense.

The use of iron is a measure of comparative civilization and enterprise. The iron of the Valley is far more important and useful to it than all the gold and silver mines of the whole world would be. The abundance of this valuable ore indicates the high rank this region is to take as a leader of future civilization.

The first group of rocks that contain animal remains hold veins of copper of great purity and unusual abundance in the